5 Colo. Code Regs. § 1002-38.27
The provisions of 25-8-202(1)(a), (b) and (2); 25-8-203; 25-8-204; 25-8-207 and 25-8-402 C.R.S. provide the specific statutory authority for adoption of these regulatory amendments. The Commission also adopted, in compliance with 24-4-103(4), C.R.S., the following statement of basis and purpose.
BASIS AND PURPOSE:
The changes considered and adopted are addressed below by segment.
Page 1, Segment 1a
Page 1, Segment 2a
Page 3, Segment 8
Page 3, Segment 10a
Page 3, Segment 10b
Page 3, Segment 12
Page 3, Segment 13
Page 4, Segment 17a
Page 5, Segment 1
Page 5, Segment 2
Page 6, Segment 3
Page 7, Segment 4b
Page 7, Segment 4c
Page 7, Segment 6
Numerical standards for metals for these segments have previously been based on table values contained in Table III of the Basic Standards and Methodologies for Surface Water. Table III has been substantially revised, effective September 30, 1988. From the information available, it appears that the existing quality of these segments meets or exceeds the quality specified by the revised criteria in Table III, and new table value standards based thereon have therefore been adopted.
This new segment was established as a result of a December, 1987 hearing to remove it from the listing for tributaries with an aquatic life cold water class 1 classification and classify it aquatic life cold water class 2 with no numeric standards for aquatic life. This segment still retains the water supply designation, but numeric values to protect this use were inadvertently removed along with the aquatic life standards. Table values to protect water supply therefore have been readopted for this segment.
The effect of this resegmentation is to add a water supply classification, and corresponding numeric standards, to Brush Creek and Filter Gulch. Although the water in these streams is not currently used for water supply, the evidence indicates that there is a potential future use for water supply in the Denver system, particularly should the Kassler Water Treatment Plant be reopened. In addition, there was evidence of a hydrologic connection to ground water that could potentially be used in the Denver system.
The Commission rejected a proposal by Martin Marietta to apply the standards only at the point of water supply intake, in part because the evidence indicated that the precise point on intake into the Denver system cannot be predicted at this time. However, the Commission did adopt a footnote specifying that the standards for Brush Creek and Filter Gulch apply only at the downstream of the Martin Marietta property line. The evidence indicates that the entire reach of both streams above the property line is located on Martin Marietta property, and that there is no foreseeable use of the water for water supply purposes before it leaves the Martin Marietta property.
This resegmentation has been adopted to provide increased protection for fish species located in the new segment 11b which are relatively rare in Colorado. Four species of the fish community, the Johnny darter, The Iowa darter, the common shiner and the northern redbelly dace are relatively rare in Colorado. Of these four species only the Johnny darter is common in more than two or three waters in the entire state. Only in West Plum Creek and tributaries are those species relatively common.
West Plum Creek is unique in the South Plate drainage. It is the only transition zone stream that does not receive large pollutant loadings. A water is a transition stream in the region where the stream leaves the mountains and enters the plains region of Colorado. The highest diversity of fish species is normally found in this transition reach. The four species noted above all seem to require cool, clear water, slower currents with rooted aquatic vegetation.
These species have generally disappeared in other front range transition streams where nutrient loadings from domestic sewage plants are common. These waters include Boulder Creek, the Cache la Poudre and the Saint Vrain. Although one or two of these species may be found in some of these waters, only in the West Plum Creek system is the native fish assemblage still intact.
The use, a diverse native fish community, is still present in the West Plum Creek system. Protection for the use was not present without this resegmentation. Most tributaries were class 2 warm water with no standards. Because of the lack of appropriate numeric standards, discharge permits for entities discharging to most tributaries of West Plum Creek would not include restrictions for parameters such as chlorine and ammonia, which are toxic to fish. To provide needed protection for these populations the Commission has adopted numeric standards for all tributaries of West Plum Creek.
Table III of the Basic Standards and Methodologies for Surface Water has been substantially revised, effective September 30, 1988. The Metropolitan Denver Sewage Disposal District No. 1 (Metro District) requested that the new Table III be applied to segment 15 as soon as possible because the Metro District renewal discharge permit sets forth a compliance schedule requiring compliance with a water quality-based effluent limitation for silver based on the old Table III methodology. Application of the new Table III methodology will result in calculation of a less restrictive effluent limitation for silver that can be met without additional treatment facilities. The Basic Standards and Methodologies for Surface Water also provide for the development of site specific and ambient quality-based standards in lieu of the table values. The Commission has adopted such standards for mercury and zinc.
The ambient quality-based chronic standard for dissolved mercury is 0.4 ug/l which is equal to the 85th percentile of the available data. The acute standard for mercury is the table value of 2.4 ug/l. In addition to presenting data supporting a chronic ambient quality-based standard of 0.4 ug/l for mercury, the Metro District presented evidence at the hearing that the methylmercury concentrations in fish flesh from fish is segment 15 ranged between 0.19 and 0.29 mg/kg. This is well below the FDA limit of 1 mg/kg. Thus, the Commission concludes that the ambient-based chronic limit of 0.4 ug/l dissolved mercury protects the classified uses of segment 15 and that no additional treatment is necessary to meet this standard.
The Metro District also presented evidence in the hearing that 1.0 ug/l mercury is the lowest level that can be reliably achieved with specified limits of precision and accuracy during routine laboratory operating conditions. Based on this evidence, the Metro District requested that a "practical quantification limit" (PQL) equal to 1.0 ug/l be established for mercury for this stream segment.
The Commission declined to modify the ambient quality-based standard to incorporate the 1.0 ug/l PQL at this time, principally because the PQL concept has not previously been applied to Colorado water quality standards, and the Commission is not yet persuaded that its adoption on this site-specific basis is necessary or appropriate. The Commission agreed to consider this issue further at its February, 1989 hearing on the South Plate water quality standards. In the meantime, the Division may take the appropriateness of a mercury PQL into account in considering appropriate discharge permit limits for the Metro District.
For zinc, acute and chronic equations differing from the aquatic life protection formulas in the Basic Standards were adopted. The equations are based on revised water quality criteria for zinc which were published in 1987 by the U.S. Environmental Protection Agency. This new criteria document was published after the "Metals Committee" had completed its work in preparing its recommended actions for the amendments to the Basic Standards. The Table III zinc standards for agriculture and water supply are being adopted without change.
Application of the new Table III and the site-specific standards for mercury and zinc will provide the level of protection necessary to assure the maintenance of the use classification assigned to segment 15. (warm water aquatic life class 2, agriculture, water supply and recreation class 2).
Table III of the Basic Standards and Methodologies for Surface Water has been substantially revised, effective September 30, 1988. Kodak Colorado Division requested that the new table be applied to segment 12 as soon as possible because the Kodak renewal discharge permit sets forth a compliance schedule requiring compliance with a water quality-based effluent limitation for silver based on the old Table III methodology. This effluent limit represented a 50% reduction in the concentration of silver. This limit could not be met with existing wastewater treatment facilities. Application of the new Table III will result in calculation of a less restrictive effluent limitation for silver that can be met without the addition of additional treatment facilities. Application of the new Table III will provide the level of protection necessary to assure the maintenance of the use classifications (recreation class 2, warm water aquatic life class 2 and agriculture) assigned to Segment 12.
LIST OF PARTY PARTICIPANTS TO THE OCTOBER, 1988 SOUTH PLATE PUBLIC RULEMAKING HEARING
5 CCR 1002-38.27